Endotyping chronic rhinosinusitis based on olfactory cleft mucus biomarkers.

Background: Although chronic rhinosinusitis (CRS) is considered the most treatable form of olfactory dysfunction, there has been relatively little clinical attention focused on assessing endotypes as they pertain to olfactory loss.

Objectives: The goal of this study was to explore inflammatory endotypes in CRS using an unsupervised cluster analysis of olfactory cleft (OC) biomarkers in a phenotype-free approach.

Methods: Patients with CRS were prospectively recruited and psychophysical olfactory testing, Questionnaire of Olfactory Dysfunction (QOD-NS), and bilateral OC endoscopy were obtained. Mucus was collected from the OC and evaluated for 26 biomarkers using principal component analysis. Cluster analysis was performed using only OC biomarkers and differences in olfactory measures were compared across clusters.

Results: A total of 198 subjects (128 with CRS and 70 controls) were evaluated. Evaluation of OC biomarkers indicated 6 principal components, explaining 69.50% of the variance, with type 2, mixed type 1/T17-cell, growth factor, and neutrophil chemoattractant inflammatory signatures. A total of 10 clusters were identified that differed significantly in frequency of controls, and subjects with CRS with nasal polyps, and subjects with CRS without nasal polyps across the clusters (likelihood ratio test, χ=178.64; P < .001). Olfactory measures differed significantly across clusters, including olfactory testing, QOD-NS, and OC endoscopy (P < .001 for all).

Conclusions: Clustering based solely on OC biomarkers can organize patients into clinically meaningful endotypes that discriminate between subjects with CRS and controls. Validation studies are necessary to confirm these findings and further refine olfactory endotypes.